1. Field of the Invention
The present invention generally relates to tools and equipment used in the construction industry, and more specifically relates to devices for mixing and consolidating concrete. Even more specifically, the present invention relates to concrete vibrators.
2. Description of the Prior Art
In the construction industry, it is frequently necessary to lay a large area of concrete. Concrete is a mixture of cement, sand and stone. Lime is an ingredient in cement, and water is added to the mixture to form a mix or slurry.
After the wet concrete has been poured, it is common practice in the industry to vibrate the concrete. The ingredients of concrete do not flow easily. Concrete vibrators are introduced into the mix and send out shock waves. The shock waves unlock the ingredients and allow the concrete mix to flow while moving the entrapped air out. Concrete vibrators are used to consolidate the concrete and remove air pockets and voids which would otherwise compromise the strength and integrity of the hardened concrete.
Conventional concrete vibrators are well known in the art, such as described and shown in Applicant's U.S. Pat. No. 6,811,297 (Oswald) and U.S. Patent Application Publication No. 2002/0131323 (Oswald), the disclosure of each of which is incorporated herein by reference.
When a concrete vibrator is lowered into poured wet concrete to consolidate it, and vibrated at a frequency of about 10,000 to about 12,000 vibrations per minute, it was discovered by the inventor herein that the nose or front end of the concrete vibrator head pushes the concrete away faster than it can flow back. More specifically, as the vibrator head sinks into the wet concrete, it drills a hole in proportion to the diameter of the head and the total height of the vibration's amplitude. Wet concrete has high viscosity and is slow to move and make contact with the vibrator head to close the hole drilled by the head. This results in only a small portion (i.e., the front end) of the vibrator head coming in contact with the concrete to effectively vibrate the mix.
Physical evidence by examining a worn vibrator head shows that the nose (front end) is worn, while a short distance back from the nose, there appears to be little or no wear. This demonstrates that the vibrator head has little contact with the abrasive wet concrete. The result is that most of the shock waves are developed from the front of the vibrator head.